This invention relates generally to the field of electroncardiography and specifically to the area of long term ambulator electrocardiography generally referred to as Holter monitoring. The invention teaches a means for extending the application of conventional Holter monitoring to permit the detection and characterization of very low amplitude signals in the microvolt range which contain important clinical information not discernible from Holter apparatus of any prior art.
Examples of very low amplitude electrocardiographic signals known to be of clinical importance include so called "Late Potentials" which occur at the terminal end of the QRS complex of the ECG and indicate a vulnerability to malignant ventricular arrhythmia, as well as HIS bundle potentials whose temporal relationship to the preceding atrial and succeeding ventricular signals allow important determinations to be made as to the functional integrity of the conduction system of the heart. The investigation of other potentially useful correlates of very low amplitude ECG signals is currently a subject of intensive basic and clinical research.